Research On Hyperspectral,Polarization And 3D Shape Measurement Based On Broadband Interferometric Illumination

Spectrum,polarization and 3D shape are significant physical parameters of feature analysis for target detection.Spectrum reflects the material composition of the target.Attribute recognition and information extraction of the target can be performed with spectrum.Polarization information reflects the physical and chemical properties and anisotropy of material of the target.The analysis and identification of substances can be more accurate with polarization information.3D shape reflects the surface geometric characteristics of the target and is the basic information source for target recognition and analysis.With the trend of social development,the demand for 5D information fusion measurement of spectrum,polarization and 3D shape is increasingly urgent in the fields of industrial production,cultural relics archaeology,criminal investigation and identification,medical detection and so on.In the meanwhile,spectral imaging,polarization imaging and 3D shape measurement technologies have shown a development trend of partial cross-fusion.However,these schemes have the problems of complex measurement process,difficulty in multi-dimensional information registration and loss of resolution of simultaneous measurement.In this paper,a broadband interferometric illumination-based imaging method of spectrum,polarization and 3D shape is proposed to solve the difficulties of synchronous measurement of multi-dimensional information.The main research contents include the following aspects.The basic theories of spectral polarization imaging and 3D shape measurement are investigated.The basic theories of spectrum and polarization measurement are described,including the theoretical model of the spectrum measurement of the Fourier transform imaging spectrometer and the Stokes vector measurement based on the polarization camera,which provides theoretical guidance for the recovery and fusion of spectral polarization information.The theoretical model of fringe projection-based 3D shape measurement is studied.The theoretical model of equivalent projection is studied to provide theoretical guidance for 3D measurement.In order to solve the simultaneous measuring of spectral polarization imaging and 3D shape,a broadband interferometric illumination 5D information measurement system based on Sagnac shearing interferometer and polarization camera is proposed.The theoretical model of interference imaging based on broadband interference illumination is proposed,and the relationship between interferogram and spectral information in the case of interfering first and then imaging in the non-collimated optical path is analyzed.The theoretical formula of the interferogram is deduced.The model of obtaining the 5D information by the proposed system is established.The formulas of spectral polarization recovery and 3D measurement are then deduced.The principle of Sagnac shearing interference is studied.Aiming at the lack of the mathematical model of optical path difference affected by the thickness of beam splitter in Sagnac interferometer,the optical path difference caused by the deflection of the beam splitter and the refractive optical path in the beam splitter are analyzed.The theoretical formula of detailed optical path difference is deduced.The nonlinearity of the interferogram is analyzed by simulation,and the range of the thickness of the beam splitter is obtained according to the requirements of spectral resolution.Aiming at the problem of 3D shape modulation under broadband interferometric illumination,the concept of equivalent optical path difference(EOPD)is proposed.The relationship between EOPD and height is studied and deduced.Aiming at the problem in acquiring 5D information,the recovery algorithms of spectrum,polarization and 3D shape information are studied.In spectral recovery,firstly,non-uniform Fourier transform is proposed to solve the non-uniform sampling of interference fringes.The uniform interpolation is realized by convoluting the non-uniform interferogram with Gaussian kernel to reduce the spectral recovery error.Secondly,the formula of 1D iterative local Fourier transform(ILFT)is proposed to solve the problem that traditional Fourier transform can only obtain wavenumber coordinates in integer accuracy.ILFT can increase the calculation accuracy of wavenumber coordinates to sub-pixel.As a result,the accuracy of subsequent wavelength calibration is improved.In polarization recovery,firstly,polarization correction algorithm based on intensity similarity and polarization similarity are studied to reduce the instantaneous field of view error.Secondly,a polarization image denoising algorithm based on principal component analysis are studied to reduce the error of polarization recovery.In 3D measurement,the lens distortion correction and camera calibration algorithm are studied to provide the basis for 3D measurement.Aiming at the scale calibration of multi-dimensional information in this system,the spectral calibration,polarization calibration and 3D measurement calibration methods are studied.In spectral calibration,the high-accuracy wavenumber coordinate calculation methods is studied by spectrum refinement to improve the accuracy of wavelength calibration.In polarization calibration,aiming at the Mueller matrix error caused by the machining error of polarization array,the polarization calibration method based on multi-point calibration method is studied.Then the Muller matrices of the actual system is obtained to improve the accuracy of polarization recovery.In 3D measurement calibration,a method of transverse calibration is proposed.The relationship model between transverse calibration coefficient and camera calibration parameters is established.Transverse calibration coefficient can be acquired by camera internal and external parameters.The Sagnac interferometer and polarization camera based-5D information measurement system was designed and the experimental device was built according to the theoretical model.The actual optical path difference of the system was measured to obtain the spectral resolution.The spectral resolution is 13.73nm@450nm.In the visible band,the number of effective channels is 14.The accuracy of wavelength measurement is 0.16 nm.3D measurement results and image results of spectrum and polarization are obtained after measuring several targets.The relative error of Stokes parameters S1 and S2 are 4.6% and 5.1%,respectively.The accuracy of three-dimensional measurement is 89.76 μm.Therefore,the effectiveness of this method in 5D measurement is verified.This method integrates the functions of a spectrometer,a polarimeter,and a 3D shape measuring instrument.This method solves the problems of complex measurement process and difficult information matching in multi-dimensional information measurement by traditional methods.5D information measurement and fusion can be completed by one scan and Fourier transform,which is a new attempt in the field of optical detection technology.The proposed method provides a new research idea and technical approach for spectrum,polarization and 3D shape synchronously.